Spark plug



Sept. 30 1924.

of A. Bor-:HM

SPARK PLUG Filed Nov. 24

NVENTR. BVM

ATTORNEY.

Patented Sept. 30, 1924.

UNITED STATES osea-n. AA.- Bonnn, "onrrnwv Yoma N. Y;

A sranx Intro.

. application med novelie'r a4, 1920. lserial No. 426,242.

To all wko/m. t may concern:

Be it known that I, OSCAR A. BoEHM, a citizen of the United States ofAmerica, residing atNew York, county of New York, and State of New York,have invented certain new and useful Improvementsin Spark Plugs, ofwhich the following is a specification.

My invention relates to sparkplugs such as are used for ignitionpurposes, particularly in connection with internal combustion engines.

The object of my invention is to provide a spark plug which (without theuse ofauxiliary spark gaps) will exhibit a lumlnous effect when innormal operation, sucheiect being absent when the plug fails to operatefor any reason. Another object of the 1nvention is to provide a verysimple, strong, and inexpensive construction which will bepractically'leakproof and `free from shortcircuit troubles.

Two typical embodiments of my inventlon are illustrated b theaccompanyin drawings, in which Fig. 1 is an outside view of a sparkpluor constructed vaccording to my myention; Fig. 2 is a longitudinalsect1o n thereof on line 2-2 of Fi 1; Fig. 3 1s a cross section on line3 3 o Figs. 1 and 2; Fig. 4 is an end view looking in the direction ofthe arrow 4 in Fig. 1; Fig. 5 is a longitudinal section of another formof my invention on line 5-5 of Fig. 6, the latter being an end viewthereof ooking in the direction of the arrow 6 in Fig. 5.

The improved spark plug comprises a tubular metal body having the usualscrew thread 10 for securing the spark plug to a support, enerall the clinder head of the engine. Said bo y also as the usual an ular portion11 for the applicatlon o a wrench, and a bent wire or electrode 12 nearthe free end of the threaded portion 10. The inner surface of saidtubular body is tapered outwardly, its diameter being greatest at thethreaded portion 10. Preferably said tapering inner surface is made withlongitudinal ribs 13.

Within the tubular body is arranged the tubular carrier 14 for the mnerelectrode 15, the latter being a rod or wire disposed axially andpreferably -projectinl beyond the inner ends of the body and of ecarrler 14,

l'in operation.

indicate that no spark is being produced.

the outer electrode 12 being in this case located to one side of theinner or central electrode. This carrier 14 is made of glass or othersuitable resistant material which is a non-conductor of electricity andpervious to light (transparent or translucent). The outer surface of thecarrier 14 is tapered at thel same angle as the inner surface of themetal body, or approximately so, and a portion of said carrier has anexternal diameter greaterthan the smallest internal diameter of themetal body (at the outer end), so that the carrier 14 may be wedgedtightly within the metal body, as shown. A layer 16 of suitable cementis placed between the adjacent surfaces of the body and of the carrier.The .ribs 13 form grooves which cause the cement to'dry more quickly, inthe manufacture of the plug. The bore of carrier 14 of larger diameterthan the electrode 15, leaving a free space or chamber 17 between thesaid electrode and the wall of the carrier.

The inner end of the carrier 14 is open, so

tween the electrodes 12, 15. The 4outer end of the tubular carrier 14 isclosed in any suitable manner, as by means of a metal cap 18 fitted tosaid end and to the threaded outer end 15 of the electrode 15, a filling19 of suitable cement being appliedat this point to hold said electrodein place firmly. The threaded end 15 also receives the wire connectionand clamping nut which have not been shown, as they may be of usualconstruction.

A 'spark plug of this construction will not crack, is practicallyleakproof, and will not short-circuit, and is inexpensive tomanufacture. Every time a spark 'um s be tween the electrodesl2, 15,thec am er 17 will become luminous, and since the carrier 14 is perviousto light, the luminous ect will be plainly visible while the engine isAbsence of this effect will It will be noted that my invention affords aready means for testing or watching the operation of the spark plugcontinuously, without disconnecting the `plug ,from the circuit andwithout the use of auxiliary les spark gaps or like expedients whichincrease the consumption ot current or have other drawbacks.

The carrier 14 of Figs. 1 to 4 is tapered for the full. length of themetal body and cemented to the entire inner surface of said body. lnFigs. 5 and 6, the carrier'l has a contracted inner portion 14'. whichis spacedv from the metal body to form an annular chamber 20 open at theinner end, this arrangement being preferred in many cases. `lin thissecond form of my .invention the carrier 14 is cemented to the innersurface of the metal body onlyffor a portion of the length of said body.The ribs 13 in this case need not extend to that portion of the metalbody which is adjacent to the contracted portion '14". Another di'erenceconsists in the fact that in Figs.

5 and 6, the inner end of the carrier is even with the inner end ot themetal body, Where- .Micasa as in Figs. 1 to 4 the inner end of thecarrier 14 projects beyond the inner end ofthe inetalv body.

Various modifications may be made Without departingfrom the nature of myinvention as set forth in the appended claim. l claim:

A spark plug comprising a tubular body adapted for connection With asupport and having an outwardly tapering innen surface provided withlongitudinal ribs, a tubular carrier closed at its outer end and vopenat its inner end, said carrier being set Within said body and having atapered outer surface corresponding to the tapered inner surface ofsaidbody, and an electrode extendingv through said 4carrier and supportedthereby.

lin testimony whereof I have aHiXed my.

signature.

OSCAR A. BOEHM.

